1. Field of the Invention
The present invention relates to a supporting bearing means for a rotary vertical shaft, comprising a supporting bearing member attached to the shaft and arranged coaxially with respect to said shaft, said supporting bearing member having an inner cylindrical surface arranged with a radial clearance with respect to the shaft and a downwardly-facing annular slide face bearing against at least one stationary bearing body, said cylindrical surface surrounding an annular space containing liquid lubricant and being limited radially inwardly by means of a stationary screen surrounding the shaft.
2. The Prior Art
The above-mentioned stationary screen, which is hereafter called the "sleeve", constitutes the inner sealing wall for an annular oil chamber in which the supporting bearing works. Between the sleeve and the supporting bearing body there is formed an annular gap. As the supporting bearing body rotates, the oil is forced into the gap through friction in the oil. When certain critical speeds are achieved, unstable conditions and turbulence arise in the oil and the oil is thrown out beyond the sleeve. The turbulence can be counteracted by reducing the gap. If an unstable flow is to be avoided when the oil is of the usual vescosity and the gap has the usual linear speed, the width of the gap may be 2 mm at the most. Taking into consideration that sleeve diameters of more than 2 m are very common, it is clear that the provision of a sufficiently small gap may involve great difficulties from the point of view of manufacture.
Furthermore, it has been found that the small gap width -- which is a condition for laminar flow -- involves great sensitivity to jerks of the shaft. Jerks will result in variation of the gap width between a minimum value and maximum value so that a pumping effect arises in the gap. If the gap width then is small, the pulsating pressure increases will be so great that oil may easily be pumped out of the gap.